Why is a pesticide (fluoride) added to tap water and is claimed to be good for children's teeth?

Proven claim: A specfic Fluoride is used in water where natural Fluoride in water is not present. Consuming this fluoridated water will allow the enamel of developing teeth, primary and permanent, to be harder and resistant to dental caries. This has been proven with numerous scientific studies and reduced cavities dramatically since the 1950's. Use of bottled water has increased dental caries.

Amount matters: Anything, even water or oxygen, is a poison in too large a concentration. Fluoride is being debated in pesticides because it raises the Fluoride levels in our waterways too high because of the large amounts used in farming that run off into the streams in rain storms. Fluoride in toothpaste is at a concentration that reduces cavities significantly, but won't poison the individual.

Not the same thing: Like a lot of substances (oxygen, vitamin c, water) the correct small amount can be helpful, and too much can be poisonous. It takes at least 3x the recommended dosage of Fluoride over an extended time for there to be a problem. Despite lots of fearmongering by some groups the scientific facts are that when used correctly Fluoride causes no health problems and only protects teeth.